15.01.2024 Views

CompTIA A+ Certification All-in-One Exam Guide

  • No tags were found...

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

rail power from a PSU may continue to operate but will do so at reduced

frame rates. That means your games won’t play well, but the computer will

function in other capacities. See Chapter 17, “Display Technologies,” for the

scoop on power-hungry video cards.

No power supply can turn 100 percent of the AC power coming from the

power company into DC current, so all power supplies provide less power to

the system than the wattage that they draw from the wall. The difference is

lost in heat generation. The amount of this differential is advertised on the

box. ATX12V 2.0 standards require a power supply to be at least 70 percent

efficient, but many power supplies operate with better than 80 percent

efficiency.

Power supplies are typically graded for their efficiency under a voluntary

standards program called 80 Plus. Under 80 Plus, power supplies are rated

from 80 percent to 94 percent efficiency for a given load and badged with

“metal labels” such as Bronze (85 percent), Gold (90 percent), or Titanium

(94 percent) levels. These levels are achieved within a narrow range of watts

provided, while lower levels of efficiency are achieved at higher and lower

power draw. Power and efficiency curves are usually provided in the power

supply documentation. More efficiency can tell you how many watts the

system draws to supply sufficient power to the PC in actual use. The added

efficiency means the power supply wastes less power, saving you money.

EXAM TIP The CompTIA A+ 1001 exam does not require you to figure

precise wattage needs for a particular system. When building a PC for a

client, however, you do need to know this stuff!

One common argument these days is that people buy power supplies that

provide far more wattage than a system needs and therefore waste power.

This is untrue. A power supply provides only the amount of power your

system needs. If you put a 1500-W power supply into a system that needs

only 250 W, that big power supply will put out only 250 W to the system. So

buying an efficient, higher-wattage power supply gives you two benefits.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!